1. Field of the Invention
The present invention relates to an organic electroluminescent device and its manufacturing method.
2. Description of the Related Art
Organic electroluminescent devices have been developed ever since C. W. Tang et al. published xe2x80x9cOrganic Electroluminescent Diodesxe2x80x9d, Applied Physics Lett. 51(12), pp. 913-915, Sep. 21, 1987.
Tang et al. reported an electroluminecent device of a stacked structure using tris (8-quinolinol aluminum) in an emitting layer and a triphenyldiamine derivative in a hole-transporting layer. This stacked structure has advantages in that the injection efficiency of holes into the emitting layer can be improved, that electrons injected from a cathode can be blocked to increase the efficiency of exciton production from charge recombination, and that the excitons into the emitting layer can be confined. A multi-layered structure such as a double layered structure composed of a hole-injecting and transporting layer and an electron-transporting and emitting layer or a triple layered structure composed of a hole-injecting and transporting layer, an emitting layer and an electron-injecting and transporting layer is well known as an organic electroluminescent device. In order to increase the recombination efficiency of injected holes and electrons, various improvements have been introduced into the structure and fabrication process of the multi-layered structure.
In the above-described prior art organic electroluminescent device, however, since there are steps at the edges of the lower electrodes (anode), the portions of the organic layers such as the hole-transporting layer, the emitting layer and the electron-transporting layer in proximity to the steps of the lower electrodes become thinner. Particularly, when the organic layers whose thickness is usually about 100 nm becomes thinner in the proximity of the steps of the lower electrodes, a short-circuit would occur between the lower electrodes and the upper electrodes (cathodes) through the thinner portions of the organic layers, to damage the organic electroluminescent device. Additionally, since the organic electroluminescent device is subject to wettability by water, the brightness and life-time characteristics would be deteriorated by the thinner organic layers.
It is an object of the present invention to provide an organic electroluminescent device capable of suppressing the thinner portions of the organic layers.
Another object is to provide a method for manufacturing the above-mentioned organic electroluminescent device.
According to the present invention, in an organic electroluminescent device, a plurality of striped grooves are formed on an insulating substrate along a first direction. A plurality of lower electrodes are substantially buried in the striped grooves. An organic layers are formed on the insulating substrate and the lower electrodes. A plurality of striped upper electrodes are formed on the organic layers along a second direction different from the first direction.
Also, in a method for manufacturing an organic electroluminescent device, a plurality of striped grooves are formed in an insulating substrate along a first direction. Then, a photoresist pattern layer is formed have elements each formed on protrusions of the insulating substrate sandwiched by the grooves of the insulating substrate. Then, a conductive layer made of indium tin oxide (ITO), for example, is deposited on the photoresist pattern layer and in the grooves of the insulating substrate by a sputtering process. Then, a lift-off operation is performed upon the photoresist pattern layer to remove the photoresist pattern layer and a first part of the conductive layer on the photoresist pattern layer, thereby leaving a second part of the conductive layer buried in the grooves of the insulating substrate as lower electrodes. Then, an organic layers are formed on the insulating substrate and the lower electrodes. Finally, a plurality of striped upper electrodes are formed on the organic layers along a second direction different from the first direction.